Measuring Stratigraphic Congruence Across Trees, Higher Taxa, and Time.
Measuring Stratigraphic Congruence Across Trees, Higher Taxa, and Time.
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DOI：
10.1093/sysbio/syw039
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发表时间：
2016-09
影响因子：
6.5
通讯作者：
Wills MA
中科院分区：
文献类型：
--
作者：
O'Connor A;Wills MA
分支顺序与化石谱系首次出现时间的一致性可以用多种指标来量化。良好的匹配是树木准确时间校准的先决条件，而在大样本的枝形图中，一致性指数的分布支持了化石记录中时间和分类完整性模式的主张。目前应用最广泛的地层一致性指标是地层一致性指数（SCI）、修正的曼哈顿地层测度（MSM*）和间隙过剩比（GER）（及其衍生物，即拓扑格尔和修正格尔）。许多因素被认为对这些指数有不同的偏差，一些实证和模拟研究解决了一些假定的相互作用。本研究将这两种方法结合起来，量化了8个变量（分类群数量、树木平衡、树木分辨率、首次出现日期范围、FO日期重心、FO日期变异性、现存分类群百分比和无化石记录分类群百分比）对可能值分布的影响（对所有5个指数）。我们的经验数据集包括横跨整个显生宙的647个已发表的动植物进化图，并对这些数据进行了建模，包括进化枝的平均年龄（作为进化枝年龄的代理）、进化枝的分类等级及其所属的高级分类类群的影响。迄今为止，FO年代的重心还没有被研究过，在我们的经验研究中，这与地层一致性的一些测量结果有很强的相关性（头重脚轻的枝具有更好的一致性）。修正后的GER是最不容易受偏倚影响的指数。各指数在高等分类群间存在显著差异；节肢动物的一致性较低，四足动物的一致性较高。地层一致性——无论如何测量——在整个显生宙也有所不同，反映了我们样品的分类组成。值得注意的是，节肢动物比例高的时期整体一致性比四足动物比例高的时期差。[化石校正;间隙过剩比；曼哈顿地层计量学；分子钟;地层一致。)
The congruence between the order of cladistic branching and the first appearance dates of fossil lineages can be quantified using a variety of indices. Good matching is a prerequisite for the accurate time calibration of trees, while the distribution of congruence indices across large samples of cladograms has underpinned claims about temporal and taxonomic patterns of completeness in the fossil record. The most widely used stratigraphic congruence indices are the stratigraphic consistency index (SCI), the modified Manhattan stratigraphic measure (MSM*), and the gap excess ratio (GER) (plus its derivatives; the topological GER and the modified GER). Many factors are believed to variously bias these indices, with several empirical and simulation studies addressing some subset of the putative interactions. This study combines both approaches to quantify the effects (on all five indices) of eight variables reasoned to constrain the distribution of possible values (the number of taxa, tree balance, tree resolution, range of first occurrence (FO) dates, center of gravity of FO dates, the variability of FO dates, percentage of extant taxa, and percentage of taxa with no fossil record). Our empirical data set comprised 647 published animal and plant cladograms spanning the entire Phanerozoic, and for these data we also modeled the effects of mean age of FOs (as a proxy for clade age), the taxonomic rank of the clade, and the higher taxonomic group to which it belonged. The center of gravity of FO dates had not been investigated hitherto, and this was found to correlate most strongly with some measures of stratigraphic congruence in our empirical study (top-heavy clades had better congruence). The modified GER was the index least susceptible to bias. We found significant differences across higher taxa for all indices; arthropods had lower congruence and tetrapods higher congruence. Stratigraphic congruence—however measured—also varied throughout the Phanerozoic, reflecting the taxonomic composition of our sample. Notably, periods containing a high proportion of arthropods had poorer congruence overall than those with higher proportions of tetrapods. [Fossil calibration; gap excess ratio; manhattan stratigraphic metric; molecular clocks; stratigraphic congruence.]